A voltage comparator (hereinafter referred to as a comparator) is a commonly used circuit in complementary metal oxide semiconductor (CMOS) circuit design (e.g. in analog circuit design). As an example, comparators are used in analog-to-digital converters (ADCs). A comparator produces an output voltage in response to a potential difference between its input terminals, which may be referred to an input differential voltage. If a potential difference between its first input terminal and its second input terminal is positive, the comparator may output a first output voltage (e.g. a logical HIGH or binary logic 1). On the other hand, if a potential difference between its first input terminal and its second input terminal is negative, the comparator may output a second output voltage (e.g. a logical LOW or binary logic 0). A comparator can be implemented using an open-loop operational amplifier or a latched comparator, as examples.
Design of a comparator circuit may require a trade-off among various aspects, including power consumption, speed (e.g. the time it takes for the comparator to produce the correct output after a potential difference is presented at its inputs), circuit layout area, accuracy (e.g. the minimum input potential difference required for the comparator to make a correct decision), complexity of implementation, and scalability with CMOS technology nodes, as examples. It may be desirable to have comparator circuits that are able to operate at high speeds (e.g. for high frequency applications) even for small input differential voltages (e.g. about 1 mV or below). It may also be desirable to have comparator circuits that consume low power, require a low supply voltage, and have low design complexity.